The technology of the present disclosure relates to an optical scanning apparatus, an image forming apparatus including the optical scanning apparatus, and a method of adjusting a resonance frequency at an oscillating mirror unit in the optical scanning apparatus.
Conventionally, a resonance-type optical scanning apparatus has been known, which includes the oscillating mirror unit and a torsion bar unit that supports the oscillating mirror unit. In this type of optical scanning apparatus, the oscillating mirror unit is made to resonate by a piezoelectric element or the like to have a large swinging angle of the oscillating mirror unit. A resonance frequency at the oscillating mirror unit depends on the moment of inertia around the swing axis of the oscillating mirror unit and the mass of the oscillating mirror unit and the like. There is a problem that, when the resonance frequency at the oscillating mirror unit is significantly deviated from a target frequency, the swinging angle of the oscillating mirror unit falls below a target value, and a desired optical scanning property cannot be obtained. Therefore, various technologies for adjusting the resonance frequency at the oscillating mirror unit have been proposed so far.
As an example, proposed is a technology of adjusting the resonance frequency at the oscillating mirror unit by applying a droplet made from a resin material on one side face of the oscillating mirror unit and curing the droplet.